The Big Interview – Dr David Cavan

Dr David Cavan is an experienced diabetes physician who has expertise in all areas of diabetes management, with particular interests in intensive management of type 1 diabetes and in supporting lifestyle change to manage and reverse type 2 diabetes.

He actively promotes self-management and has been closely involved in the development of education programmes for people with diabetes, and is also author of successful books on self-management of type 2 diabetes.

You have just released a book about managing type 1 diabetes can you explain more about it?

My aim in this book is to provide a person with type 1 diabetes with all the information and tools they need to take control of the condition. I cover the basics such as how to make sure you are on the right insulin doses and advice on diet as well as the pros and cons of using an insulin pump and new technologies. But equally importantly, I explore the emotional impact of living with type 1 diabetes, how the condition affects so many areas of life – and how normal life’s ups and downs affect diabetes, and try to provide reassurance and a measure of hope.

You have previously written about type 2 diabetes, what are the main differences you think there are between managing type 1 and type 2?

I approach them as fundamentally two very different conditions. Type 2 diabetes is largely a result of our modern day lifestyles and so is best treated – and in some cases reversed – my modifying lifestyles. Type 1 diabetes is an autoimmune condition that causes a hormone deficiency. As with other hormone deficiencies, the treatment is directed at replacing the missing hormone, in this case insulin.

However, unlike nearly every other hormone deficiency, insulin treatment is very complex, precisely because of the impact of everyday life on the amount of insulin required.

What makes your dietary approach so unique?

I am not sure my dietary approach is unique but it is different from the conventional advice for type 1 diabetes. With the advent of modern insulin analogues around 20 years ago, there was a notion that a person with type 1 diabetes can eat whatever they like, as long as they inject the correct dose of insulin.

This even influenced the name of DAFNE – dose adjustment for normal eating. The years since then have convinced me that this is just not true. Yes, you can eat a large bowl of pasta with over 100 grams of carbohydrate and inject a large dose of insulin to cover it, but even using the most advanced insulin pumps, it will be very difficult to maintain glucose levels in the normal range for several hours afterwards. A large dose of insulin also increases the risk of hypoglycaemia.

At the end of the day, type 1 diabetes, like type 2 diabetes, is a form of carbohydrate intolerance as the body cannot naturally deal with carbohydrates. Looking at it in that way, doesn’t it just make sense to advise people with the condition to avoid large amounts of carbohydrate? A low carb diet means less insulin needs to be injected, with less risk of hypos and crucially also less risk of excess weight gain. It also tends to exclude a lot of processed foods and is therefore very healthy eating.

What are the main food myths that people nowadays still believe are good for their health?

I think the biggest myth is that fat is bad, followed by the belief that natural sugars are good. I see this particularly in Bermuda, where I spent six months last year, setting up a programme for type 2 diabetes, and where the food environment is heavily influenced by the US market. It is almost impossible to find full fat yoghurt, people buy processed ‘egg whites’ to avoid eating the yolks and there are plenty of low fat salad dressings that include a lot of sugar to give them taste.

There, and in the UK, people think they are doing themselves good by drinking fruit juice or making a fruit smoothie – both are essentially sugar-sweetened beverages. This hasn’t been helped by the official UK dietary advice which includes fruit juice as one of your ‘five a day’. The same advice suggests that eating a banana is a good idea, yet for someone with diabetes, this could push their glucose to a very high level.

How did your role as the Director of Policy for the International Diabetes Federation help contribute to your ideas in regard to diabetes management?

More than anything, it opened my eyes as to how fortunate we are to live in a society that provides universal health care, where no one with diabetes has to worry about paying to see their GP or to get blood tests done. Nor do they have to worry about whether they can afford insulin. Contrast that with the situation in many countries of the world, including the USA, where some people just cannot afford the treatment that will keep them healthy.

While I was at the IDF, I co-ordinated a global survey of access to medicines. Shockingly, in many of the poorest countries of the world, even inexpensive medications such as metformin are not readily available or affordable. So, when thinking about diabetes management, while it is great to get excited about potential of new technologies such as continuous glucose monitoring, I am always mindful of how we can make things work well for people who live in less well-resourced countries, where even glucose test strips may not be available. That is why, I include sections in the book on the use of ‘old-fashioned’ insulins that are rarely used nowadays in the UK in type 1 diabetes – because I want the book to be useful and relevant in as many countries of the world as possible.

It also reinforced my belief that the best way to make progress against type 2 diabetes is by effective lifestyle management programmes, rather than relying on medications, that many people just cannot afford.

As a low carb advocate, what would you say to people who argue against it, like the rising cholesterol argument?

I would challenge them to explain why they would advise a high carbohydrate diet to a person with carbohydrate intolerance. Would they also advocate a milk diet to someone with lactose intolerance, or a bread diet to someone with gluten intolerance? And I would point them to the increasingly powerful data that not only is a low carb diet better than any medication in reducing HbA1c in type 2 diabetes, it also saves huge amounts of money through less usage of medications. Finally, I would point out that the majority of people who adopt a low carb diet see an improvement in cholesterol levels.

Yes, it does rise in some people, and we need to better understand why and the implications of that happening, which may not be harmful. Every drug has side effects, statins for example, increase the risk of developing type 2 diabetes, yet they are still prescribed to millions of people for many years. As with any type of treatment, one has to weight up the benefits against the risk of possible adverse effects in each individual case, rather than dismiss the treatment out of hand.

How would you counter arguments linking low carb diets to DKA in people with type 1 diabetes?

I am not aware of any evidence that low carb diets are linked to DKA in people with type 1 diabetes. The ‘argument’ results from a fundamental misunderstanding, even amongst health professionals, of the difference between ketosis and ketoacidosis. I even heard a dietitian from Diabetes UK use this argument to advise against a low carb diet on a radio interview some years ago.

I would counter the argument by explaining the difference, as I do in the book. Ketosis is a normal physiological state where the body is deriving its energy mainly from fat metabolism. Insulin levels are by definition appropriately low, and blood acidity and glucose levels are normal. Ketoacidosis is an abnormal metabolic state that arises from lack of insulin, with abnormally high levels of acidity and glucose in the blood.

Diabetes UK in May 2017 came out and said it did “not recommend low-carb diets to people with type 1 diabetes” because “there is no strong evidence to say that a low-carb diet is safe or effective for people with type 1 diabetes”. How would you respond to this?

I would point to their 2018 nutrition guidelines which state that ‘there is no convincing evidence for a recommended ideal amount of carbohydrate for maintaining long term glycaemic control in type 1 diabetes.’ Thus by their argument, there is no evidence for either a low or high carbohydrate approach. I would also refer them to one of their founding fathers, Dr RD Lawrence, who had type 1 diabetes himself, and whose standard recommendation was a carbohydrate intake of 100 grams daily.

What is the future for low carb diets and type 1 diabetes?

I think it is the unstoppable way forward. Thanks to the ability of people to connect via online forums, I increasingly have patients come to me to say they have put themselves on a low carb diet, and usually they are pleased with the result. When I applaud them, they are often quite surprised as they say they have been discouraged in the past by professionals from going low carb, but it made so much sense that they did it anyway.

What’s been your biggest achievement?

There are two recent ones that come to mind, but in both cases they were not my achievements, but the combination of many people working together. The first is the establishment of a low carb programme in Bermuda, which has a massive 17% prevalence of type 2 diabetes, and where we are already seeing 20% of participants reverse their diabetes. The second is my book, Take Control of Type 1 Diabetes, that I largely wrote while I was in Bermuda. It was the most difficult piece of writing I have ever done – much harder than I anticipated, but the feedback I have had so far has been very positive. While I had the task of doing the writing, many of the ideas within it come from the great teamwork within the diabetes unit in Bournemouth, where I worked for so many years.

Take Control of Type 1 Diabetes by Dr Cavan in partnership with Diabetes.co.uk is available from the Diabetes.co.uk/shop price £14.99